The feasibility of using ultra-narrow band (UNB) antennas for internet-of-things applications is discussed. An analysis aimed at evaluating the antenna miniaturisation limits when there are almost no bandwidth requirements is performed. Both numerical and experimental results show that, carefully taking into account the metal conductivity, it is possible to obtain miniature antennas with good impedance matching, UNB, and acceptable efficiency. As a representative example, a wearable on-body antenna outperforming by 10 dB in terms of total efficiency a commercial solution is presented.